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The Missouri River is the longest
river A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake or another river. In some cases, a river flows into the ground and becomes dry at the end of its course without reaching another body of wate ...

river
in
North America North America is a continent A continent is any of several large landmasses. Generally identified by convention (norm), convention rather than any strict criteria, up to seven geographical regions are commonly regarded as continen ...

North America
. Rising in the
Rocky Mountains The Rocky Mountains, also known as the Rockies, are a major mountain range A mountain range is a series of mountains ranged in a line and connected by high ground. A mountain system or mountain belt is a group of mountain ranges with similari ...

Rocky Mountains
of the Eastern Centennial Mountains of Southwestern
Montana Montana () is a state State may refer to: Arts, entertainment, and media Literature * ''State Magazine'', a monthly magazine published by the U.S. Department of State * The State (newspaper), ''The State'' (newspaper), a daily newspaper ...

Montana
, the Missouri flows east and south for before entering the
Mississippi River The Mississippi River is the second-longest river and chief river A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake or another river. In some cases, a river flows into the ground and b ...

Mississippi River
north of
St. Louis St. Louis () is the second-largest city in Missouri Missouri is a state State may refer to: Arts, entertainment, and media Literature * ''State Magazine'', a monthly magazine published by the U.S. Department of State * The State ( ...

St. Louis
,
Missouri Missouri is a state State may refer to: Arts, entertainment, and media Literature * ''State Magazine'', a monthly magazine published by the U.S. Department of State * The State (newspaper), ''The State'' (newspaper), a daily newspaper in ...

Missouri
. The river drains a sparsely populated,
semi-arid A semi-arid climate, semi-desert climate, or steppe climate is the climate Climate is the long-term average of weather, typically averaged over a period of 30 years. More rigorously, it is the mean and variability of meteorological variables ove ...
watershed Watershed is a hydrological term, which has been adopted in other fields in a more or less figurative sense. It may refer to: Hydrology * Drainage divide, the line that separates neighbouring drainage basins ** European watershed * Drainage basin, ...

watershed
of more than 500,000 square miles (1,300,000 km2), which includes parts of ten U.S. states and two Canadian provinces. Although nominally considered a tributary of the Mississippi, the Missouri River above the confluence is much longer than the Mississippi above the confluence and carries a comparable volume of water. When combined with the lower Mississippi River, it forms the world's fourth longest river system. For over 12,000 years, people have depended on the Missouri River and its
tributaries A tributary, or affluent, is a stream A stream is a body of water (Lysefjord) in Norway Norway, officially the Kingdom of Norway,Names in the official and recognised languages: Bokmål Bokmål (, ; literally "book tongue") ...
as a source of sustenance and transportation. More than ten major groups of
Native American Native Americans may refer to: Ethnic groups * Indigenous peoples of the Americas, the pre-Columbian peoples of North and South America and their descendants * Native Americans in the United States * Indigenous peoples in Canada, the indigenous p ...
s populated the watershed, most leading a nomadic lifestyle and dependent on enormous
bison Bison are large, even-toed ungulate The even-toed ungulates (Artiodactyla , ) are ungulate Ungulates ( ) are members of the diverse clade A clade (; from grc, , ''klados'', "branch"), also known as a monophyletic group or natural gro ...

bison
herds that roamed through the
Great Plains The Great Plains (french: Grandes Plaines), sometimes simply "the Plains", is a broad expanse of in . It is located west of the and east of the , much of it covered in , and . It is the southern and main part of the , which also include the ...
. The first Europeans encountered the river in the late seventeenth century, and the region passed through Spanish and French hands before becoming part of the United States through the
Louisiana Purchase The Louisiana Purchase (french: Vente de la Louisiane, translation=Sale of Louisiana) was the acquisition of the Louisiana (New France), territory of Louisiana by the United States from French First Republic, Napoleonic France in 1803. In retur ...

Louisiana Purchase
. The Missouri River was one of the main routes for the westward expansion of the United States during the 19th century. The growth of the
fur trade The fur trade is a worldwide industry dealing in the acquisition and sale of animal fur Fur is a thick growth of hair Hair is a protein filament In biology Biology is the natural science that studies life and living organi ...
in the early 19th century laid much of the groundwork as trappers explored the region and blazed trails.
Pioneer Pioneer commonly refers to a settler who migrates to previously uninhabited or sparsely inhabited land. In the United States pioneer commonly refers to an American pioneer, a person in American history who migrated west to join in settling and deve ...
s headed west ''en masse'' beginning in the 1830s, first by
covered wagon The covered wagon, also called the prairie schooner, was a vehicle usually made out of wood Wood is a porous and fibrous structural tissue found in the Plant stem, stems and roots of trees and other woody plants. It is an organic material ...

covered wagon
, then by the growing numbers of
steamboat upright=1.35, Dutch river steam-tugboat ''Mascotte II'' A steamboat is a boat that is propelled primarily by steam power from Stott Park Bobbin Mill, Cumbria, England A steam engine is a heat engine In thermodynamics Thermod ...

steamboat
s that entered service on the river. Conflict between settlers and Native Americans in the watershed led to some of the most longstanding and violent of the
American Indian Wars The American Indian Wars, also known as the American Frontier Wars, the First Nations Wars in Canada (french: Guerres des Premières Nations) and the Indian Wars were fought by European governments and colonists, and later by the United States an ...
. During the 20th century, the Missouri River basin was extensively developed for irrigation, flood control, and the generation of
hydroelectric power Hydroelectricity, or hydroelectric power, is electricity produced from hydropower Hydropower (from el, ὕδωρ, "water"), also known as water power, is the use of falling or fast-running water to produce electricity or to power machin ...
. Fifteen dams impound the
main stem In hydrology Hydrology (from Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approxi ...
of the river, with hundreds more on tributaries.
Meander A meander is one of a series of regular sinuous curves in the channel of a river or other watercourse. It is produced as a watercourse the s of an outer, concave bank () and deposits sediments on an inner, convex bank which is typically a . Th ...

Meander
s have been cut off and the river channelized to improve navigation, reducing its length by almost from pre-development times. Although the lower Missouri valley is now a populous and highly productive agricultural and industrial region, heavy development has taken its toll on wildlife and fish populations as well as water quality.


Course

From the Rocky Mountains, three streams rise to form the headwaters of the Missouri River: *The longest source stream begins near
Brower's Spring Brower's Spring is a spring in the Centennial Mountains of Beaverhead County Montana that was marked by a surveyor in 1888 as the ultimate headwaters of the Missouri River and thus the fourth longest river in the world, the -long Mississippi River, ...
in southwest
Montana Montana () is a state State may refer to: Arts, entertainment, and media Literature * ''State Magazine'', a monthly magazine published by the U.S. Department of State * The State (newspaper), ''The State'' (newspaper), a daily newspaper ...

Montana
, above sea level on the southeastern slopes of Mount Jefferson in the
Centennial Mountains The Centennial Mountains are the southernmost sub-range of the Bitterroot Range in the United States states of Idaho and Montana. The Centennial Mountains include the Western and Eastern Centennial Mountains. The range extends east from Monida Pass ...

Centennial Mountains
. From there it flows west then north; runs first in
Hell Roaring Creek Hell Roaring Creek is a fast-running creek in southern Montana Montana () is a U.S. state, state in the Mountain states, Mountain West region of the United States. It is bordered by Idaho to the west; North Dakota and South Dakota to the ...
then west into the Red Rock; swings northeast to become the
Beaverhead River The Beaverhead River is an approximately tributary of the Jefferson River The Jefferson River is a tributary A tributary, or affluent, is a stream or river that flows into a larger stream or main stem (or parent) river or a lake. A tributar ...
; and finally joins with the
Big Hole The Kimberley Mine or Tim Kuilmine ( af, Groot Gat) is an open-pit and underground mine in Kimberley, South Africa Kimberley is the capital and largest city of the Northern Cape Province of South Africa South Africa, officially the ...
to form the
Jefferson River The Jefferson River is a tributary A tributary, or affluent, is a stream or river that flows into a larger stream or main stem (or parent) river or a lake. A tributary does not flow directly into a sea or ocean. Tributaries and the main stem r ...
. *The
Firehole River The Firehole River is located in northwestern Wyoming Wyoming () is a state State may refer to: Arts, entertainment, and media Literature * ''State Magazine'', a monthly magazine published by the U.S. Department of State * The State (ne ...
, which originates in northwest
Wyoming Wyoming () is a U.S. state, state in the Mountain states, Mountain West subregion of the Western United States. The List of U.S. states and territories by area, 10th largest state by area, it is also the List of U.S. states and territories b ...
at
Yellowstone National Park Yellowstone National Park is an American national park located in the western United States, largely in the northwest corner of Wyoming and extending into Montana and Idaho. It was established by the U.S. Congress and signed into law by ...

Yellowstone National Park
's Madison Lake, joins with the
Gibbon River The Gibbon River flows east of the Continental Divide in Yellowstone National Park, in northwestern Wyoming, the Northwestern United States. Along with the Firehole River, it is a major tributary of the Madison River, which itself is a tributary o ...

Gibbon River
to form the
Madison River The Madison River is a headwater tributary of the Missouri River, approximately 183 miles (295 km) long, in Wyoming and Montana. Its confluence with the Jefferson River, Jefferson and Gallatin River, Gallatin rivers near Three Forks, Montana ...
. *The
Gallatin River The Gallatin River is a tributary of the Missouri River, approximately 120 mi (193 km long), in the U.S. states of Wyoming and Montana. It is one of three rivers, along with the Jefferson River, Jefferson and Madison River, Madison, ...
flows out of Gallatin Lake which is also in Yellowstone National Park. The Missouri River officially starts at the confluence of the Jefferson and Madison in
Missouri Headwaters State Park Missouri Headwaters State Park is a List of Montana state parks, Montana state park that marks the official start of the Missouri River. It includes the Three Forks of the Missouri National Historic Landmark, designated in 1960 because the site is ...
near
Three Forks, Montana Three Forks is a city in Gallatin County, Montana Montana () is a U.S. state, state in the Mountain states, Mountain West region of the United States. It is bordered by Idaho to the west; North Dakota and South Dakota to the east; Wyomi ...

Three Forks, Montana
, and is joined by the Gallatin a mile (1.6 km) downstream. It then passes through
Canyon Ferry Lake Canyon Ferry Lake is a reservoir (water), reservoir on the Missouri River near Helena, Montana and Townsend, Montana. It is Montana's third largest body of water, covering 35,181 acres (142 km²) and 76 miles (122 km) ...
, a reservoir west of the
Big Belt Mountains The Big Belt Mountains are a section of the Rocky Mountains The Rocky Mountains, also known as the Rockies, are a major mountain range in western North America. The Rocky Mountains stretch in great-circle distance, straight-line distance from t ...
. Issuing from the mountains near
Cascade Cascade, Cascades or Cascading may refer to: Science and technology Science *Cascade waterfalls, or series of waterfalls * Cascade, the CRISPR-associated complex for antiviral defense (a protein complex) * Cascade (grape), a type of fruit * Bioche ...
, the river flows northeast to the city of
Great FallsGreat Falls may refer to: Communities * Great Falls, Montana * Somersworth, New Hampshire or Great Falls * Great Falls, South Carolina * Great Falls, Virginia ** Great Falls Park Waterfalls

* Great Falls (Hamilton, Ontario), Canada * Great Fall ...

Great Falls
, where it drops over the Great Falls of the Missouri, a series of five substantial waterfalls. It then winds east through a scenic region of canyons and badlands known as the Missouri Breaks, receiving the
Marias River The Marias River is a tributary of the Missouri River, approximately 210 mi (338 km) long, in the U.S. state of Montana Montana () is a U.S. state, state in the Mountain states, Mountain West region of the United States. It is ...
from the west then widening into the
Fort Peck Lake Fort Peck Lake, or Lake Fort Peck, is a major reservoir in Montana, formed by the Fort Peck Dam on the Missouri River. The lake lies in the eastern prairie region of Montana approximately east of Great Falls, Montana, Great Falls and north of Bil ...
reservoir a few miles above the confluence with the
Musselshell River The Musselshell River is a tributary A tributary or affluent is a stream or river that flows into a larger stream or main stem (or parent) river or a lake. A tributary does not flow directly into a sea or ocean. Tributaries and the main stem riv ...
. Farther on, the river passes through the
Fort Peck Dam The Fort Peck Dam is the highest of six major s along the , located in northeast in the , near , and adjacent to the community of . At in length and over in height, it is the largest dam in the , and creates , the fifth largest artificial l ...
, and immediately downstream, the Milk River joins from the north. Flowing eastward through the plains of eastern Montana, the Missouri receives the Poplar River from the north before crossing into
North Dakota North Dakota () is a U.S. state In the , a state is a , of which there are currently 50. Bound together in a , each state holds al jurisdiction over a separate and defined geographic territory where it shares its with the . Due to th ...
where the
Yellowstone River The Yellowstone River is a tributary of the Missouri River, approximately long, in the Western United States. Considered the principal tributary of upper Missouri, via its tributaries, it drains an area stretching from the Rocky Mountains in the ...

Yellowstone River
, its greatest tributary by volume, joins from the southwest. At the confluence, the Yellowstone is actually the larger river. The Missouri then meanders east past Williston and into
Lake Sakakawea Lake Sakakawea is a large reservoir in the West North Central States, north central United States, impounded in 1953 by Garrison Dam, a U.S. Army Corps of Engineers dam located in the Missouri River basin in central North Dakota. Named for the Sh ...
, the reservoir formed by
Garrison Dam Garrison Dam is an earth-fill embankment dam in Pakistan Pakistan, . Pronounced variably in English language, English as , , , and . officially the Islamic Republic of Pakistan, is a country in South Asia. It is the world's List of countr ...
. Below the dam the Missouri receives the
Knife River The Knife River is a tributary of the Missouri River, approximately 120 mi (193 km) long, in North Dakota in the United States. Knife is an English translation of the Native American name. It rises in west central North Dakota, in the ...
from the west and flows south to Bismarck, the capital of North Dakota, where the Heart River joins from the west. It slows into the
Lake Oahe Lake Oahe () is a large reservoir A reservoir (; from French language, French ''réservoir'' ) is most commonly an enlarged natural or artificial lake created using a dam to water storage, store water. Reservoirs can be created in a number of ...

Lake Oahe
reservoir just before the
Cannonball River The Cannonball River ( lkt, Íŋyaŋwakağapi Wakpá) is a tributary of the Missouri River, approximately long, in southwestern North Dakota in the United States. It rises in the Little Missouri National Grassland, in the badlands north of Amidon ...
confluence. While it continues south, eventually reaching
Oahe Dam The Oahe Dam is a large earthen dam on the Missouri River, just north of Pierre, South Dakota, Pierre, South Dakota, United States. The dam creates Lake Oahe, the fourth-largest man-made reservoir in the United States. The reservoir stretches up t ...
in
South Dakota South Dakota () (Sioux The Sioux or Oceti Sakowin (; Dakota Dakota may refer to: * Dakota people, a sub-tribe of the Sioux ** Dakota language, their language From this origin, Dakota may also refer to: Places United States * Dakot ...

South Dakota
, the
Grand Grand may refer to: People with the name * Grand (surname) Grand * Cedric Grand (born 1976), Swiss bobsledder * Gil Grand (born 1968), Canadian country music singer * Jean-Pierre Grand (born 1950), French politician * Pascale Grand (born 1967), ...
, Moreau and
Cheyenne River The Cheyenne River ( lkt, Wakpá Wašté; "Good River"), also written ''Chyone'', referring to the Cheyenne people who once lived there, is a tributary of the Missouri River in the U.S. states of Wyoming and South Dakota. It is approximately ...
s all join the Missouri from the west. The Missouri makes a bend to the southeast as it winds through the Great Plains, receiving the
Niobrara RiverNiobrara may refer to: * Niobrara, Nebraska * Niobrara County, Wyoming * Niobrara River * Niobrara National Scenic River * Niobrara Formation, a geological unit * Niobrara Township, Knox County, Nebraska {{geodis All dams are on the upper half of the river above Sioux City; the lower river is uninterrupted due to its longstanding use as a shipping channel.


Navigation

"[Missouri River shipping] never achieved its expectations. Even under the very best of circumstances, it was never a huge industry."
~Richard Opper, former Missouri River Basin Association executive director
Boat travel on the Missouri began with the wood-framed canoes and bull boats that Native Americans used for thousands of years before the colonization of the Great Plains introduced larger craft to the river. The first steamboat on the Missouri was the ''Independence'', which started running between St. Louis and Keytesville, Missouri around 1819.Demoth, p. 101 By the 1830s, large mail and freight-carrying vessels were running regularly between Kansas City and St. Louis, and many traveled even farther upstream. A handful, such as the ''Western Engineer'' and the ''Yellowstone (steamboat), Yellowstone'', could make it up the river as far as eastern Montana. During the early 19th century, at the height of the fur trade, steamboats and keelboats travelled nearly the whole length of the Missouri from Montana's rugged Missouri Breaks to the mouth, carrying beaver and buffalo furs to and from the areas the trappers frequented. This resulted in the development of the Mackinaw boat#Development, Missouri River mackinaw, which specialized in carrying furs. Since these boats could only travel downriver, they were dismantled and sold for lumber upon their arrival at St. Louis. Water transport increased through the 1850s with multiple craft ferrying pioneers, emigrants and miners; many of these runs were from St. Louis or Independence to near Omaha. There, most of these people would set out overland along the large but shallow and unnavigable Platte River, which pioneers described as "a mile wide and an inch deep" and "the most magnificent and useless of rivers". Steamboat navigation peaked in 1858 with over 130 boats operating full-time on the Missouri, with many more smaller vessels.Dyer, p. 2 Many of the earlier vessels were built on the Ohio River before being transferred to the Missouri. Side-wheeler steamboats were preferred over the larger sternwheelers used on the Mississippi and Ohio because of their greater maneuverability. The industry's success, however, did not guarantee safety. In the early decades before man controlled the river's flow, its sketchy rises and falls and its massive amounts of sediment, which prevented a clear view of the bottom, wrecked some 300 vessels. Because of the dangers of navigating the Missouri River, the average ship's lifespan was only about four years. The development of the Transcontinental and Northern Pacific Railroad, Northern Pacific Railroads marked the beginning of the end of steamboat commerce on the Missouri. Outcompeted by trains, the number of boats slowly dwindled, until there was almost nothing left by the 1890s. Transport of agricultural and mining products by barge, however, saw a revival in the early twentieth century.


Passage to Sioux City

Since the beginning of the 20th century, the Missouri River has been extensively engineered for water transport purposes, and about 32 percent of the river now flows through artificially straightened channels. In 1912, the USACE was authorized to maintain the Missouri to a depth of from the Port of Kansas City to the mouth, a distance of . This was accomplished by constructing levees and wing dams to direct the river's flow into a straight, narrow channel and prevent sedimentation. In 1925, the USACE began a project to widen the river's navigation channel to ; two years later, they began dredging a deep-water channel from Kansas City to Sioux City. These modifications have reduced the river's length from some in the late 19th century to in the present day. Construction of dams on the Missouri under the Pick-Sloan Plan in the mid-twentieth century was the final step in aiding navigation. The large reservoirs of the Mainstem System help provide a dependable flow to maintain the navigation channel year-round, and are capable of halting most of the river's annual freshets. However, high and low water cycles of the Missouri – notably the protracted early-21st-century drought in the Missouri River basin and historic floods in 1993 and 2011 – are difficult for even the massive Mainstem System reservoirs to control. In 1945, the USACE began the Missouri River Bank Stabilization and Navigation Project, which would permanently increase the river's navigation channel to a width of and a depth of . During work that continues to this day, the navigation channel from Sioux City to St. Louis has been controlled by building rock dikes to direct the river's flow and scour out sediments, sealing and cutting off meanders and side channels, and dredging the riverbed. However, the Missouri has often resisted the efforts of the USACE to control its depth. In 2006, the U.S. Coast Guard stated that commercial barge tows ran aground in the Missouri River because the navigation channel had been severely silted. The USACE was blamed for failing to maintain the channel to the minimum depth. In 1929, the Missouri River Navigation Commission estimated the amount of goods shipped on the river annually at 15 million tons (13.6 million metric tons), providing widespread consensus for the creation of a navigation channel. However, shipping traffic has since been far lower than expected – shipments of commodities including produce, manufactured items, lumber, and oil averaged only 683,000 tons (616,000 t) per year from 1994 to 2006. By tonnage of transported material, Missouri is by far the largest user of the river accounting for 83 percent of river traffic, while Kansas has 12 percent, Nebraska three percent and Iowa two percent. Almost all of the barge traffic on the Missouri River ships sand and gravel dredged from the lower of the river; the remaining portion of the shipping channel now sees little to no use by commercial vessels. For navigation purposes, the Missouri River is divided into two main sections. The Upper Missouri River is north of Gavins Point Dam, the last hydroelectric dam of List of dams in the Missouri River watershed, fifteen on the river, just upstream from Sioux City, Iowa. The Lower Missouri River is the of river below Gavins Point until it meets the Mississippi just above
St. Louis St. Louis () is the second-largest city in Missouri Missouri is a state State may refer to: Arts, entertainment, and media Literature * ''State Magazine'', a monthly magazine published by the U.S. Department of State * The State ( ...

St. Louis
. The Lower Missouri River has no hydroelectric dams or lock (water transport), locks but it has a plethora of wing dams that enable barge traffic by directing the flow of the river into a , channel. These wing dams have been put in place by and are maintained by the U.S. Army Corps of Engineers, and there are no plans to construct any locks to replace these wing dams on the Missouri River.


Traffic decline

Tonnage of goods shipped by barges on the Missouri River has seen a serious decline from the 1960s to the present. In the 1960s, the USACE predicted an increase to per year by 2000, but instead the opposite has happened. The amount of goods plunged from in 1977 to just in 2000. One of the largest drops has been in agricultural products, especially wheat. Part of the reason is that irrigated land along the Missouri has only been developed to a fraction of its potential. In 2006, barges on the Missouri hauled only of products which is equal to the ''daily'' freight traffic on the Mississippi. Drought conditions in the early 21st century and competition from other modes of transport – mainly railroads – are the primary reason for decreasing river traffic on the Missouri. The USACE's failure to consistently maintain the navigation channel has also hampered the industry. Efforts are being made to revive the shipping industry on the Missouri River, because of the efficiency and cheapness of river transport to haul agricultural products, and the overcrowding of alternative transportation routes. Solutions such as expanding the navigation channel and releasing more water from reservoirs during the peak of the navigation season are under consideration. Drought conditions lifted in 2010, in which about were barged on the Missouri, representing the first significant increase in shipments since 2000. However, flooding in 2011 closed record stretches of the river to boat traffic – "wash[ing] away hopes for a bounce-back year". There are no lock and dams on the lower Missouri River, but there are plenty of wing dams that Jetty, jettie out into the river and make it harder for barges to navigate. In contrast, the upper Mississippi has List of locks and dams of the Upper Mississippi River, 29 locks and dams and averaged 61.3 million tons of cargo annually from 2008 to 2011, and its locks are closed in the winter.


Ecology


Natural history

Historically, the thousands of square miles that comprised the floodplain of the Missouri River supported a wide range of plant and animal species. Biodiversity generally increased proceeding downstream from the cold, subalpine headwaters in Montana to the temperate, moist climate of Missouri. Today, the river's riparian zone consists primarily of Hibiscus tiliaceus, cottonwoods, willows and Platanus, sycamores, with several other types of trees such as maple and Fraxinus, ash.Benke and Cushing, p. 436 Average tree height generally increases farther from the riverbanks for a limited distance, as land next to the river is vulnerable to soil erosion during floods. Because of its large sediment concentrations, the Missouri does not support many aquatic invertebrates. However, the basin supports about 300 species of birds and 150 species of fish, some of which are endangered species, endangered such as the pallid sturgeon. The Missouri's aquatic and riparian habitats also support several species of mammals, such as minks, river otters, beavers, muskrats, and raccoons.Benke and Cushing, p. 438 The World Wide Fund For Nature divides the Missouri River watershed into three freshwater ecoregions: the Upper Missouri, Lower Missouri and Central Prairie. The Upper Missouri, roughly encompassing the area within Montana, Wyoming, southern Alberta and Saskatchewan, and North Dakota, comprises mainly semiarid shrub-steppe grasslands with sparse biodiversity because of Ice Age glaciations. There are no known endemic species within the region. Except for the headwaters in the Rockies, there is little precipitation in this part of the watershed. The Middle Missouri ecoregion, extending through Colorado, southwestern Minnesota, northern Kansas, Nebraska, and parts of Wyoming and Iowa, has greater rainfall and is characterized by temperate forests and grasslands. Plant life is more diverse in the Middle Missouri, which is also home to about twice as many animal species. Finally, the Central Prairie ecoregion is situated on the lower part of the Missouri, encompassing all or parts of Missouri, Kansas, Oklahoma and Arkansas. Despite large seasonal temperature fluctuations, this region has the greatest diversity of plants and animals of the three. Thirteen species of crayfish are endemic to the lower Missouri.


Human impacts

Since river commerce and industrial development began in the 1800s, human activity has severely polluted the Missouri and degraded its water quality. Most of the river's floodplain habitat is long gone, replaced by irrigated agricultural land. Development of the floodplain has led to increasing numbers of people and infrastructure within areas at high risk of inundation. Levees have been constructed along more than a third of the river to keep floodwater within the channel, but with the consequences of faster stream velocity and a resulting increase of peak flows in downstream areas. Fertilizer runoff, which causes elevated levels of nitrogen and other nutrients, is a major problem along the Missouri River, especially in Iowa and Missouri. This form of pollution also affects the upper Mississippi, Illinois River, Illinois and Ohio Rivers. Low oxygen levels in rivers and the vast Gulf of Mexico dead zone at the end of the Mississippi Delta are both results of high nutrient concentrations in the Missouri and other tributaries of the Mississippi. Channelization of the lower Missouri waters has made the river narrower, deeper and less accessible to riparian flora and fauna. Many dams and bank stabilization projects have been built to help convert of Missouri River floodplain to agricultural land. Channel control has reduced the volume of sediment transported downstream by the river and eliminated critical habitat for fish, birds and amphibians. By the early 21st century, declines in populations of native species prompted the U.S. Fish and Wildlife Service to issue a biological opinion recommending restoration of river habitats for federally endangered bird and fish species. The USACE began work on ecosystem restoration projects along the lower Missouri River in the early 21st century. Because of the low use of the shipping channel in the lower Missouri maintained by the USACE, it is now considered feasible to remove some of the levees, dikes, and wing dams that constrict the river's flow, thus allowing it to naturally restore its banks. By 2001, there were of riverside floodplain undergoing active restoration. Restoration projects have re-mobilized some of the sediments that had been trapped behind bank stabilization structures, prompting concerns of exacerbated nutrient and sediment pollution locally and downstream in the northern Gulf of Mexico. A 2010 United States National Research Council, National Research Council report assessed the roles of sediment in the Missouri River, evaluating current habitat restoration strategies and alternative ways to manage sediment. The report found that a better understanding of sediment processes in the Missouri River, including the creation of a "sediment budget" – an accounting of sediment transport, erosion, and deposition volumes for the length of the Missouri River – would provide a foundation for projects to improve water quality standards and protect endangered species.


National Wild and Scenic River

Several sections of the Missouri River were added to the National Wild and Scenic Rivers System from Fort Benton, Montana, Fort Benton to Fred Robinson Bridge, Robinson Bridge, Gavins Point Dam to Ponca State Park and Fort Randall Dam to Lewis and Clark Lake. A total of of the river were designated including of wild river and of scenic river in Montana. of the river is listed as recreational under the National Wild and Scenic Rivers System.


Tourism and recreation

With over of open water, the six reservoirs of the Missouri River Mainstem System provide some of the main recreational areas within the basin. Visitation has increased from 10 million visitor-hours in the mid-1960s to over 60 million visitor-hours in 1990. Development of visitor facilities was spurred by the Federal Water Project Recreation Act of 1965, which required the USACE to build and maintain boat ramps, campgrounds and other public facilities along major reservoirs. Recreational use of Missouri River reservoirs is estimated to contribute $85–100 million to the regional economy each year. The Lewis and Clark National Historic Trail, some long, follows nearly the entire Missouri River from its mouth to its source, retracing the route of the Lewis and Clark Expedition. Extending from Wood River, Illinois, in the east, to Astoria, Oregon, in the west, it also follows portions of the Mississippi and Columbia Rivers. The trail, which spans through eleven U.S. states, is maintained by various federal and state government agencies; it passes through some 100 historic sites, notably archaeological locations including the Knife River Indian Villages National Historic Site. Parts of the river itself are designated for recreational or preservational use. The Missouri National Recreational River consists of portions of the Missouri downstream from Fort Randall and Gavins Point Dams that total . These reaches exhibit islands, meanders, sandbars, underwater rocks, Riffle-pool sequence, riffles, Snag (ecology), snags, and other once-common features of the lower river that have now disappeared under reservoirs or have been destroyed by channeling. About forty-five steamboat wrecks are scattered along these reaches of the river. Downstream from Great Falls, Montana, about of the river course through a rugged series of canyons and badlands known as the Missouri Breaks. This part of the river, designated a U.S. National Wild and Scenic River in 1976, flows within the Upper Missouri Breaks National Monument, a preserve comprising steep cliffs, deep gorges, arid plains, badlands, archaeological sites, and whitewater rapids on the Missouri itself. The preserve includes a wide variety of plant and animal life; recreational activities include boating, rafting, hiking and wildlife observation. In north-central Montana, some along over of the Missouri River, centering on
Fort Peck Lake Fort Peck Lake, or Lake Fort Peck, is a major reservoir in Montana, formed by the Fort Peck Dam on the Missouri River. The lake lies in the eastern prairie region of Montana approximately east of Great Falls, Montana, Great Falls and north of Bil ...
, comprise the Charles M. Russell National Wildlife Refuge. The wildlife refuge consists of a native northern Great Plains ecosystem that has not been heavily affected by human development, except for the construction of Fort Peck Dam. Although there are few designated trails, the whole preserve is open to hiking and camping. Many U.S. national parks, such as Glacier National Park (U.S.), Glacier National Park, Rocky Mountain National Park,
Yellowstone National Park Yellowstone National Park is an American national park located in the western United States, largely in the northwest corner of Wyoming and extending into Montana and Idaho. It was established by the U.S. Congress and signed into law by ...

Yellowstone National Park
and Badlands National Park are, at least partially, in the watershed. Parts of other rivers in the basin are set aside for preservation and recreational use – notably the Niobrara National Scenic River, which is a protected stretch of the Niobrara River, one of the Missouri's longest tributaries. The Missouri flows through or past many National Historic Landmarks, which include Missouri Headwaters State Park, Three Forks of the Missouri, Fort Benton, Montana, Big Hidatsa Village Site, Fort Atkinson (Nebraska), Fort Atkinson, Nebraska and Arrow Rock Historic District.


See also

* ''Across the Wide Missouri (book)'' * List of longest main-stem rivers in the United States * List of crossings of the Missouri River * List of populated places along the Missouri River * Missouri National Recreational River * U.S. Army Corps of Engineers * Montana Stream Access Law * Montana Wilderness Association * Sacagawea * Arabia Steamboat Museum * Container on barge


Notes


References


Works cited

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Further reading

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External links


USGS Columbia Environmental Research Center: Missouri River

Interactive Maps and Air photos for Missouri River Dams and Reservoirs



U.S. Army Corps of Engineers - Kansas City District

U.S. Army Corps of Engineers - Omaha District
* {{Good article Missouri River, Tributaries of the Mississippi River Borders of Iowa Borders of Kansas Borders of Missouri Borders of Nebraska Borders of South Dakota Geography of Omaha, Nebraska Rivers of Yankton County, South Dakota Rivers of Gallatin County, Montana Bodies of water of Broadwater County, Montana Rivers of Lewis and Clark County, Montana Bodies of water of McCone County, Montana Bodies of water of Roosevelt County, Montana Mississippi River watershed Rivers of Iowa Rivers of Kansas Rivers of Missouri Rivers of Montana Rivers of Nebraska Rivers of North Dakota Rivers of South Dakota Waterways in Omaha, Nebraska